The prior art is replete with liquid spray guns of the type comprising a body assembly having a liquid passageway with an outlet end opening through an outlet end of a nozzle portion, which body assembly has a first air passageway having an outlet end around the outlet end of the liquid passageway shaped to direct high velocity air against liquid flowing out of the outlet end of the liquid passageway to propel the liquid away from the nozzle portion while shaping the liquid into a generally conical stream about an axis; the body assembly including an air cap having horns projecting past the outlet end of the nozzle on opposite sides of the axis, and having a second air passageway extending to outlet passageways and apertures spaced along the horns from the outlet end of the nozzle and facing opposite sides of the axis, which horn outlet passageways and apertures are positioned to direct high velocity air against opposite sides of a stream of liquid formed by air flowing through the first air passageway to reshape that generally conical stream into a wide elongate stream that is directed against a surface to which the liquid (e.g., paint) is being applied. U.S. Pat. No. 1,751,787 (Binks); U.S. Pat. No. 1,990,823 (Gustopsson); U.S. Pat. No. 3,746,253 (Walberg); U.S. Pat. No. 5,090,623 (Burns et al.); U.S. Pat. No. 5,102,051 (Smith et al); U.S. Pat. No. 5,209,405 (Robinson et al); U.S. Pat. No. 5,322,221 (Anderson); U.S. Pat. No. 5,344,078 (Fritz et al.) and U.S. Pat. No. 5,803,367 (Heard et al.) and U.S. patent application Publication No. US 2002/0148910 A1 published Oct. 17, 2002, provide illustrative examples.
Many patterns of outlet passageways and apertures in the horns of such spray guns have been used in an attempt to form a wide elongate stream of liquid that is as uniform as possible in width and in the amount of liquid delivered per unit time along its length to facilitate uniform application of the liquid to a surface. In all known liquid spray guns of this type the air outlet passageways along the horns are cylindrical, typically having been formed by drilling into the horns on the air cap after the air cap is formed. Air flows out of such cylindrical passageways in generally cylindrical streams that impact the side of the stream of liquid. While such cylindrical air streams from cylindrical passageways placed on the horns can form a wide elongate stream of liquid, the uniformity of the width of that stream and the uniformity in the amount of liquid delivered per unit time along its length are not as good as may be desired because such cylindrical air streams do not apply a uniform amount of energy across their diameters against the side of the stream of liquid.